The putting green demands turfgrass with highly specialized characteristics. The grass must withstand extremely low mowing heights, often less than 0.125 inches, while maintaining a dense and uniform canopy. This aggressive management is necessary to achieve the speed and smoothness required for a true ball roll. Only a few select grass species are suitable due to the unique physical stresses of constant cutting, rolling, and foot traffic.
Climate Factors Determining Grass Selection
The primary factor determining the type of grass used for a golf green is the regional climate, specifically the temperature range in which the grass can perform optimally. Turfgrasses are broadly categorized into two groups based on their physiological adaptation to temperature, which dictates survival during summer heat or winter cold.
Cool-season turfgrasses grow best when air temperatures are between 60 and 75 degrees Fahrenheit, thriving in temperate and northern regions. Conversely, warm-season turfgrasses require temperatures between 80 and 95 degrees Fahrenheit for optimum growth. Planting cool-season grass in a warm region will cause it to suffer severe stress or death from summer heat.
Warm-season grasses enter a state of dormancy and turn brown when temperatures drop below approximately 50 degrees Fahrenheit. This makes them unsuitable for northern climates where golfers expect a green surface year-round. The “Transition Zone,” where both types struggle during peak seasons, presents the greatest challenge for turf managers.
Cool-Season Grasses: The Bentgrass Standard
The standard grass species used on greens in cool-season and transition zones is Creeping Bentgrass (Agrostis stolonifera). This turf is prized for its fine leaf texture and its ability to tolerate the continuous, close-cut maintenance required for a high-quality putting surface. It spreads laterally by stolons, allowing the plant to form a dense mat capable of quick recovery from damage.
Modern cultivars have been selectively bred for improved density, disease resistance, and better heat tolerance, allowing their use further south. Varieties like ‘Penn A-1’, ‘Penncross’, and ‘Pure Distinction’ are examples of advanced bents chosen for superior performance under stress.
A common challenge is the natural invasion of Annual Bluegrass (Poa annua), which appears due to its prolific seed production and tolerance for low mowing. Annual Bluegrass is generally less desirable because it produces seed heads that disrupt the ball roll and is less tolerant of heat and drought than modern bentgrass varieties.
Warm-Season Grasses: The Bermudagrass Option
In southern and subtropical regions where summer temperatures exceed the tolerance of bentgrass, hybrid Bermudagrass (Cynodon dactylon) is the dominant choice for greens. It is highly valued for its exceptional heat and drought resistance, making it ideal for hot, sunny climates. Bermudagrass is a rapidly growing species that recovers quickly from aggressive management practices.
Ultra-dwarf hybrid Bermudagrasses are engineered for putting surfaces, tolerating mowing heights as low as 0.100 to 0.125 inches. Cultivars such as ‘TifEagle’, ‘Champion Dwarf’, and ‘MiniVerde’ were developed to provide the density and fine texture needed for a fast, true putting surface. ‘TifEagle’ is known for its extremely fine, erect leaf blades that maintain a high-speed surface.
These warm-season grasses are often overseeded with a cool-season annual grass, such as perennial ryegrass or Poa trivialis, during the winter months. This provides a green playing surface when the Bermudagrass enters its natural dormant, brown state due to cold temperatures. Aggressive management, including frequent verticutting and topdressing, is necessary to control dense growth and prevent thatch buildup.